The present invention relates to formulations useful as splice adhesives or as primers for roofing materials made from ethylene-propylene diene monomers (EPDM).
Roofing materials useful for covering large roof areas are customarily prepared in wide sheets for efficient installation. These wide sheets must be overlapped and spliced together when the roofing sheets are installed to provide uniform surfaces. Overlap splicing is often done under extreme weather conditions and the adhered sections must continue to withstand severe weather at extremes of cold and hot temperatures for many years.
Customarily roofing materials, made from plastic, rubber or ethylene propylene diene monomer (EPDM), have been spliced together on site with neoprene (polychloroprene) based contact adhesives. A well known treatise, the Handbook of Adhesives edited by Irving Skiest, published by Van Nostrand Reinhold Company, 1977 edition, at page 880, recommends the use of neoprene based adhesives on EPDM substrates. Butyl rubber based adhesives containing isocyanates and zinc oxide as the curative components are also commonly used. Another EPDM roofing adhesive is described in U.S. Pat. No. 4,640,730 and combines thermoplastic block copolymer, aromatic hydrocarbon resins, sulfur and zinc oxide.
EPDM membranes are a very popular form of single ply roofing. Often they are treated with talc, mica, or cellulosic powders to improve processing and handling of the finished membrane. Splice adhesives often adhere poorly to these treated surfaces.
The adhesives customarily used with EPDM materials, neoprene (chloroprene) adhesive and conventional butyl rubber adhesives, have some deficiencies. The neoprene adhesives may require pre-treatment of the EPDM material with an isocyanate-containing primer or with another primer such as that described in commonly assigned U.S. Pat. application Ser. No. 06/887,594 which provides a primer containing thermoplastic block copolymer, halogenated butyl rubber, aromatic hydrocarbon reinforcing resin, diphenyl quanidine secondary accelerator and solvent. This primer is used in conjunction with neoprene adhesives. The butyl rubber adhesives typically include an isocyanate component within the butyl rubber formulation. U.S. Pat. No. 4,501,842 (Uniroyal, Inc.) describes such an isocyanate-containing butyl rubber adhesive for bonding cured EPDM rubber.
Conventional neoprene adhesives exhibit poor water resistance and insufficient long term durability. The butyl rubber adhesives containing isocyanate are less stable on storage and do not perform well when used after storage. As soon as moisture is introduced into the open container the adhesion and long term stability begin to degrade and this trend worsens with continued exposure. Butyl rubber adhesives containing isocyanate show poor building tack, short open time, poor bond strength at elevated temperature and poor brushability across the application temperature range (0.degree. C. to 65.degree. C.) observed on a roofing site. Adhesives requiring pre-treatment of the EPDM substrate with primers are more cumbersome to use than adhesives needing nothing more than their own application.